The present invention relates to control systems using switches. More particularly, the present invention relates to automated activation and reset of silicon controlled rectifiers using sensors such as Optoschmitts, and other related circuits.
Many products operate with control systems that use microprocessors or mechanical switches. In an effort to control an event or process, mechanical switches are manufactured with various styles of actuators attached which, when depressed, act to regulate power or send a signal to the microprocessor. With this type of switch, not only is there physical contact but the switch itself must be mounted and actuated with some degree of precision to operate efficiently.
Microprocessors are useful in process control but require programming and additional hardwarexe2x80x94an interfacexe2x80x94to give them the capacity of controlling high voltage devices.
There is a way to effectively control events and processes and eliminate the problems mentioned above by using a silicon controlled rectifier (xe2x80x9cSCRxe2x80x9d) or thyristor.
Thyristors or silicon controlled rectifier switches can be used as a substitute for mechanical switches. SCRs, however, often require a manual reset after they have activated a target system (e.g., motor or relay), or additional circuitry to achieve reset. This manual reset has previously taken the form of a manual push button.
Improved circuits are therefore required which decrease the reliance on mechanically-activated and reset switches, and which capitalize on sensors which can automatically control electrical switches and other devices such as SCRs upon certain sensed events.
The shortcomings of the prior art are overcome, and additional advantages are provided, by the present invention which in one aspect is a control system for a target system coupled with a power source. A resettable switch is coupled between the target system and a current source/sink. A current sourcing/sinking device (e.g., an Optoschmitt sensor) is commonly coupled with the target system and the resettable switch at a common node. A sensing of a first event activates the switch to thereby activate the target system by causing a flow of current from the power source through the target system and the switch. A sensing of the second event causes the output of the current sourcing/sinking device to draw current from the target system, thereby continuing the flow of current through the target system. The drawing of current by the output of the current sourcing/sinking device from the target system removes the flow of current through the switch thereby automatically resetting the switch while the target system remains activated.
A sensing of a third event inactivates the target system by causing the output of the current sourcing/sinking device to remove the current drawn from the first terminal of the target system, thereby removing the flow of current through the target system.
In exemplary embodiments, the current sourcing/sinking device comprises an Optoschmitt sensor, and the resettable switch comprises a thyristor or a silicon controlled rectifier resettable by the removing of current therethrough.
The target system could comprise a relay for driving higher voltage devices.
In an alternate embodiment of the present invention, a single resettable switch initiated by a single event activates a plurality of target systems, each of the target systems then operable using its own, respective current sourcing/sinking device for removing current drawn therefrom upon subsequent, respective future events. This arrangement is useful when the power to each target system is to be determined at different times. If these events are to be turned off at the same time, a single Optoschmitt sensor can be used. In this arrangement, the power to the devices (assuming they operate on the same voltage) can be tied together and drawn from a single relay. The single relay can then provide power to several devices using one SCR and one relay.
In this regard, the present invention is both a system and a method for resetting a switch resettable by the removal of current therefrom, wherein the switch is used to activate a target system by providing a first current path therefrom. The current sourcing/sinking device (e.g., an Optoschmitt sensor) is used to supplant the first current path with an alternate current path thereby resetting the switch while maintaining activation of the target system. The target system continues to operate, even though the thyristor has been reset, until the Optoschmitt sensor has been deactivated.
Other embodiments of the control system of the present invention are also disclosed, including a method and control system for operating a target system requiring a current path therethrough. A first state of the Schmitt device is used to source/sink the current path to activate said target system; and a second state of the Schmitt device is used to sink/source the current path to deactivate the target system.
Finally a water tank flush/refill application of the principles disclosed herein is presented.